1. Field of the Invention
The present invention relates to an image recognition apparatus for recognizing whether an input image is an image of a predetermined category, a method of controlling the image recognition apparatus, and a storage medium.
2. Description of the Related Art
There is conventionally known a face recognition technique that extracts a face region from an image including a human face and compares the extracted face image with the face image of a specific person registered in advance, thereby performing personal recognition. This technique is used for a security purpose to, for example, permit entry to an office when a person captured by a camera is authenticated as a registered person. There is also a demand for using this technique to search for photos including identical persons. For the security purpose, the technique allows highly accurate recognition by imposing restrictions on conditions for capturing a person. In the latter case, however, the person capturing conditions are wide-ranging, resulting in a lower recognition accuracy. For example, identical persons may erroneously be determined as different persons if the face orientation, expression, and illumination at the time of photographing change between photos.
A method has been proposed to solve this problem, in which recognition is performed by registering a plurality of face images captured under various conditions. Japanese Patent Laid-Open No. 2007-249588 discloses a method of improving the recognition accuracy by registering faces in various states such as a face turned upward, a face with a beard, and a face with the mouth open from an input moving image. Japanese Patent Laid-Open No. 2009-258991 discloses a method of improving the recognition accuracy by registering a plurality of face images with different face orientations.
However, combining the conditions such as the face orientation, expression, and illumination increases the number of face images to be registered. In addition, the processing amount also increases because collation with a lot of face images needs to be done in recognition processing.